1. Field of the Invention
Controlled depth fishing has been a popular sport for many years. Controlled depth fishing methods allow fishermen to troll a lure such as a spoon, crankbait, dodger-fly combination, etc. at depths much greater that the lure would dive on its own.
Controlled depth fishing is accomplished by means of a downrigger mounted to a watercraft. The downrigger is comprised of a frame which mounts to a boat, a reel with an electric motor or hand crank mechanism, a boom extending from the boat over the water, a pulley at the end of the boom, stainless steel cable that is spooled onto the reel and threaded through the pulley at the end of the boom, and a cannonball attached to the end of the cable. The cannonball is usually constructed of lead and typically weighs between 10 pounds to 18 pounds. The downrigger may also include a counter connected to the reel and calibrated in feet to indicate to the user how far below the water surface the cannonball is tracking. FIG. 1 illustrates a typical downrigger.
To use a downrigger in controlled depth fishing, the fisherman would first allow a lure attached to a standard fishing reel and pole to troll out behind the watercraft. Typically the lure is let out about 10 to 30 feet. The fisherman would then attach the line from the rod and reel to the cannonball with a rubber band or pincher type release mechanism. The fisherman would then slowly allow the cannonball to descend into the water to a predetermined depth. The depth can be read from the counter on downriggers so equipped. In this scenario, the lure is now running at the depth of the cannonball. This depth would also be shown on the downrigger's counter. FIG. 2 illustrates the details controlled depth fishing. Note that the lure attached to the rod and reel is now being trolled at the depth of the cannonball.
When a fish strikes the lure, the strike either breaks the rubber band attaching the line to the cannonball or pulls the line out of the pincher release and allows the fisherman to fight the fish with just the rod and reel. Once the line is released from the cannonball, the downrigger no longer plays a part in the fighting and retrieval of the fish. FIG. 3 illustrates a scenario right after the rubber band has broken or pincher has released.
Controlled depth fishing has been proven to be a very effective method for catching fish species such as Salmon and Trout in the Great Lakes. It has also proved to be an effective method for catching a wide variety of fish in the ocean.
Additionally, it is well known that fish such as Salmon and Trout prefer waters of certain temperature ranges and will seek out the waters that provide these temperatures. Additionally, it has been found that fish are most likely to strike a lure traveling or trolled at a specific range of speed. Therefore, fisherman will seek a particular temperature of water and a troll at a specific speed when targeting a specific species of fish.
Most watercraft used for fishing usually includes a means for measuring water surface temperature and surface speed. However, this information usually has no bearing as to what water temperature and water speed are well below the surface at the cannonball and lure.
2. Description of the Prior Art
Over the past decade or so, there have been several electronic apparatus sold to fisherman who practice controlled depth fishing to measure the water temperature and water speed at the cannonball and lure. These systems are comprised of an underwater sensor/transmitter probe, a special downrigger cable with a plastic coating, a receiving antenna, a receiver/display unit, and a shield cable that connects the receiving antenna to the receiver/display unit, and a power cable that provides 12V boat power to the receiver/display unit.
The theory of operation of such a system is as follows:
The underwater probe unit is mechanically and electrically attached to the special coated downrigger cable as to provide a strong mechanical connection to suspend the probe, as well as provide an electrical connection such that the downrigger wire is used as a signal path to the watercraft. This connection must be wrapped in a special rubberized electrical tape or apply liquid sealant to electrically isolate the connection from the water. The probe transmits its sensed data over this cable via a low frequency RF signal—typically anywhere between 100 KHz and 500 KHz.
A drop leader of 18″-24″ typical is attached to the bottom tab of the underwater probe, and the cannonball is then attached to this leader to provide the weight necessary to hold the probe and fishing lure at a predetermined depth.
A pick-up antenna in the form of a spring with multiple turns of wire is used to receive the signal sent on the downrigger cable from the underwater probe. The downrigger cable passes through the center of the spring. The spring is also attached to a cable (usually shielded cable or coax). This antenna cable then connects to another cable (usually shielded cable or coax) which carries the signal received from the underwater probe to the receiver/display module.
The underwater probe periodically measures water temperature and speed with respect to the surrounding water; and periodically reports this information to the receiver/display unit by transmitting the sensed data via an RF signal over the coated downrigger cable.
The receiver/display module monitors the received signal, decodes the data and displays the speed and temperature as reported by the probe on the LCD display for viewing by the operator. FIG. 4 illustrates the major components of the system as well as their connectivity.
The installer replaces the ordinary downrigger cable with the special coated cable. This coated cable is then attached to the underwater sensor/transmitter probe. To make the attachment to the probe, the coating on the cable must be stripped away such that there is an electrical connection between the cable and the metal tab on the probe unit. The user would then install a thimble and barrel crimps to secure the cable to the tab. Once the barrel crimps are installed, the user would then insolate this connection with a special rubberized electrical tape to isolate the electrical connection from the water. FIG. 5 illustrates this interconnection method between the coated downrigger cable and the underwater probe. FIG. 6 illustrates this connection after rubberized electrical tape has been applied.
The spring antenna is mounted to the downrigger boom as illustrated in FIG. 7. The coated downrigger cable passes through the center of the spring antenna. The shielded cable connecting to the spring antenna is mounted to the downrigger boom—typically with nylon tie straps. The tie straps are usually positioned at least 6-10″ from the spring antenna to allow the antenna to flex and move with the downrigger cable. This is necessary so that the shielded cable is not damaged from the constant movement of the spring antenna/downrigger cable.
The antenna cable includes a connector on the end opposite the spring antenna. This connector is plugged into a second shielded cable with connectors on both ends. This cable is then routed throughout the watercraft up to the display/receiver unit, where it plugs into a connector on the receiver/display.
The receiver/display unit is mounted on the watercraft in a convenient viewing location. A third cable, the power cable, is plugged into the receiver/display unit. The opposite end of the power cable is wired directly into the 12VDC power of the watercraft.
Further, another system readily available to fisherman operates in a similar fashion to the system described above, but additionally includes a means for the underwater sensor/transmitter unit to measure ambient light intensity, water pressure, and probe battery voltage. This information is transmitted up the coated downrigger cable in addition to the speed and temperature information. The receiver/display in this system also includes provisions to decode this information and display it on the LCD screen. The receiver/display unit converts measured pressure into depth. In this system, water temperature, water speed, probe battery voltage, ambient light intensity (in percentage) and probe depth are displayed on the LCD.
Shortcomings of Prior Art:
Many fishermen have expressed great disappointment in being required to use the special coated downrigger cable to carry the underwater probe transmitted signal to the spring antenna mounted on the downrigger boom. After weeks and months of use, the coating on the cable may become damaged or frayed, thereby exposing the inner conductor to the water. When water contacts the conductor in the coated cable, the signal becomes attenuated, and at a certain depth, the system no longer operates. As an example, with new coated cable the system may operate to 200′ of water. However, when the insulating coating becomes damaged and frayed thereby exposing the inner conductor to water, system operation may be limited to 40′ or less—depending on the extent of damage to the insulating coating—again, this is due to the attenuation effects of the water on the transmitted signal. Further, this special coated cable is much more expensive than ordinary downrigger cable, and therefore it costs the user time and money to replace the coated cable. Still further, the cable is of larger diameter than ordinary cable due to the insulating coating, and this additional diameter increases the cables drag in water causing the cannonball to run much father behind the boat at normal trolling speeds as compared to a cable without the coating.
Another shortcoming is that of an underwater probe of the prior art that is large and bulky. Large probes cause additional drag in the water, and therefore cause the downrigger cannonball to track much farther behind the boat than the cannonball would track without the probe attached to the downrigger cable. Ideally, the fisherman would like the cannonball to track directly beneath the watercraft. The more drag on the system, the farther behind the watercraft the cannonball will track.
Still another shortcoming of the underwater probe of the prior art is that many times they do not track true with respect to the line of motion of the watercraft. This is due to the ferromagnetic rotor or ‘paddle wheel’ that is mounted on the side of the probe unit—causing the probe to ‘dog track’ or track at somewhat of an angle to the line of motion of the watercraft.
Yet another shortcoming of the underwater probe of the prior art is that of the wire and snap-clip attachment means of the 9V battery. This snap-clip attachment means can become damaged over time, and the wires can fatigue and break—requiring the probe to be sent in for repair.
Yet another shortcoming of the underwater probe of the prior art is that the electronics are not sealed against water damage should the O-rings that seal the battery cover fail. Once water enters the unit, the electronics become submerged in water and potential permanent failure of the electronics could occur.
Yet another shortcoming of the underwater probe of the prior art is that the housing only includes one O-ring seal to seal the battery cover to the housing. Many times the single O-ring seal becomes damaged and allows water to enter the probe.
Yet another shortcoming of the underwater probe of the prior art is that the electronics consume a fair amount of power, requiring the user to replace the 9V battery at regular intervals during use.
Yet another shortcoming of the underwater probe of the prior art is that the design is not such that it can be easily injection molded and has to be machined from tubular plastic piping such as PVC.
Yet another shortcoming of the underwater probe of the prior art is that it is not easily manufactured and requires a large amount of labor.
Yet another shortcoming of the underwater probe of the prior art is that the housing has a geometry which does not easily lend itself to applying rubberized electrical tape to create an adequate seal against water intrusion.
A shortcoming of the spring antenna of the prior art is that it does not provide adequate means to recover maximum amount of received signal due to its construction of only a few turns of wire and short length.
Yet another shortcoming of the antenna of prior art is that the spring-to-cable connection is covered with heat shrink tubing and is mechanically weak and prone to breakage.
A shortcoming of the receiver/display unit of the prior art is that while it displays the underwater probe's battery voltage, the average user does not possess the detailed knowledge required to determine at what voltage should the probe battery be replaced.
Another shortcoming of the receiver/display unit of the prior art is that there is no backlight for the LCD to be viewed at night, and if a backlight is provided, it is not user adjustable.
Another shortcoming of the receiver/display unit of the prior art is that there is no backlight for the user controls to be viewed at night, and if a backlight is provided, it is not user adjustable.
Another shortcoming of the receiver of the prior art is that the input signal receiving circuitry does not provide adequate selectivity to the specific received signal frequency.
Yet another shortcoming of the receiver/display unit of the prior art is that it does not provide a means for easy software updates such as new speed and temperature calibration tables, new software features, and the like.
Yet another shortcoming of the receiver/display unit of the prior art is that it does not provide a means for the user to calibrate the speed and temperature as reported by the probe to a separate system on the watercraft that measures surface speed and temperature.
Yet another shortcoming of the receiver/display unit of the prior art is that it requires the user to manually shut if off after use. If a user forgets to shut it off, it continues to consume boat battery power—which could lead to a dead boat battery over a period of time.
Yet another shortcoming of the receiver/display unit of the prior art is that it does not allow the user to variably adjust the averaging of displayed data to compensate for calm or wavy water conditions.
Yet another shortcoming of the receiver/display unit of prior art is that it is large and bulky thereby limiting mounting locations on the watercraft.
While the methods described above for measuring water temperature and water speed at the underwater probe as well as optionally measuring probe battery voltage, water pressure and water clarity at the probe may be suitable for the purposes for which they were designed, they would not be suitable for the purposes of the present invention, as hereinafter described.